Words I thought I'd never write: "Jackass" Johnny Knoxville has made an actual movie.

I don't mean the occasional part the actor takes in someone else's film, notably Luke Duke in 2005's "The Dukes of Hazzard." Or the string of stunts that migrated pretty much intact to the big screen from MTV's "Jackass" reality series, with "Jackass: The Movie" in 2002, followed by "Jackass Number Two" and "Jackass 3D." All lowbrow, low-budget and lucrative.

What I do mean is that "Jackass Presents: Bad Grandpa" is an evolution. The film has a story complete with a beginning, middle and end. It has some acting and emotion. And most shocking of all — it has empathy.

Which may make hard-core "Jackass" fans — the highly coveted young adult male demo that throws good money at bad entertainment all the time — shudder.

Rest easy, boys; there is still much for our man Johnny to fear. And waiting for you is that quintessential "Jackass" moment when you ask the friend or stranger next to you — between howls of laughter, it should be noted — "Is that really his …? Are those really his …?"

In "Bad Grandpa," Knoxville, now 42 and certifiably middle-aged crazy, stays very much in the danger zone. In the grand "Jackass" tradition, "Grandpa's" antics are as politically incorrect as ever — racist, sexist and salacious. Unsuspecting citizens are "caught on tape" as they are exposed to the insanity, another "Jackass" trademark. And, most important, the movie is hysterical in the worst possible ways; ones that make you feel as if a public apology is due: "So sorry, everyone."

Knoxville's brand of anarchy has been dismissed as everything from total nonsense to a real danger for those who try to replicate the pranks (all the films carry a warning label). But he's actually playing with an extreme form of performance art framed by a frat-boy, locker-room, keg-party mentality. In all that running amok that so often involves (and I don't know why) alligators, subversive social jabs can be found. Case in point: You could argue there was a subtle message to "think before you ink" in the classic "Off-Road Tattoo" bit in one of the earlier films.

Sadly, there are no alligators in "Bad Grandpa," at least that I recall, but everything else is there, including a few thoughts on the current state of our growing geriatric nation and broken families that too often leave grandparents to raise the little ones.

"Grandpa's" various bad influences have been cooked up by the original "Jackass" creative team, which in addition to Knoxville includes Jeff Tremaine and "Being John Malkovich" filmmaker Spike Jonze. The trio share screenplay credit for this docu-comedy-drama hybrid, and Tremaine, as he has from the beginning, directs.

The story is grounded in Knoxville's old-guy character, Irving Zisman, who's been used for odd scams here and there in the past. Now he's got an entire backstory.

As "Grandpa" opens, Zisman is 86 and newly widowed. To get the central gag going, there is a funeral for his late wife, Ellie (basically a coffin cameo by Catherine Keener, aged beyond recognition and as silent as the grave), with an unsuspecting choir in attendance. Zisman is thanking them for their time, making apologies for his absent daughter (Georgina Cates) and grandson Billy (Jackson Nicoll), when, like a bad penny, they turn up.

The action from this point on is driven by what, where and how to handle Grandma Ellie's dead body, and by Billy's disposal as well. He's been dumped with Grandpa while mom heads to prison, and deadbeat dad (Zia Harris) lives thousands of miles away.

A road trip and many indelicate encounters follow as the pair make their way to Billy's dad for the big handoff. The patience of many will be tested, including any female of any age, many fast food and convenience store owners, some kiddie beauty pageant contestants, a few strip-club patrons and countless random people on the street.

Some forgive the old guy, or the kid — Nicoll is a chip off the Knoxville block, and I mean that with all due respect. Some do not. One 45-year-old guy threatens to "tune Grandpa up" over a penguin debacle.

There are also a surprising number of serious and sweet moments between Billy and Grandpa. Actual family bonding takes place, in the open, for anyone to see.

Now I don't mean to suggest that "Bad Grandpa" has gone highbrow — the "Jackass" brow is just as arched as ever. And to be clear, the plot is slight. The dialogue goes from not bad to not too bad.

Still, it's amazing what a little story and a little substance add to a movie. It might not be a giant leap for mankind, but it is a small step for one old man.